Getter arrangement in color picture tube

ABSTRACT

A getter structure arrangement for a three-gun color picture cathode-ray tube is disclosed, wherein the convergence electrode structure is formed to block the neck of the tube and prevent any getter particles from migrating to the vicinity of the electron emitting cathode. The convergence electrode has an outwardly flanged rim to reduce the spacing from the inner envelope surface and has inwardly flanged beam apertures forming ridges for reducing chances of getter particles entering the convergence cup from reaching the cathode.

United States Patent Inventor Jay 11. Johnson Owensboro, Ky. Appl. No. 798,739 Filed Feb. 12, 1969 Patented Feb. 16, 1971 Assignee Kentucky Electronics, Inc.

Owensboro, Ky. a corporation of Delaware GETTER ARRANGEMENT IN COLOR PICTURE TUBE 2 Claims, 1 Drawing Fig.

US. Cl 313/181, 313/70, 313/178 Int. Cl H01j 19/70 Field 01' Search 313/69C,

[56] References Cited UNITED STATES PATENTS 2,957,106 10/1960 Moodey 3 I 3/70X 3,183.39] 5/1965 Benway 313/178X Primary Examiner- Raymond F. Hossfeld Attorney-Laurence R. Brown ABSTRACT: A getter structure arrangement for a three-gun color picture cathode-ray tube is disclosed, wherein the convergence electrode structure is formed to block the neck of the tube and prevent any getter particles from migrating to the vicinity of the electron emitting cathode. The convergence electrode has an outwardly flanged rim to reduce the spacing from the inner envelope surface and has inwardly flanged beam apertures forming ridges for reducing chances of getter particles entering the convergence cup from reaching the cathode.

GETTER ARRANGEMENT INCOLOR PICTURE TUBE THE DESCRIPTION This invention relates to color picture cathode-ray tubes having a plurality of electron guns and a convergence electrode and more particularly it relates to the arrangement of the electrodes and the getter structure in such tubes to prevent contamination of the cathode with getter particles.

in order to absorb traces of residual gasses left in the tube or later appearing during operation and thus attain a lower pressure, it is customary to provide a getter which is flashed during the final stages of evacuation of cathode-ray tubes to put a film about part of the envelope inner walls. This film remains to function during the life of the tube. However, since the getter is generally a metallic material which will contaminate the electron emitting surface of the cathode, care must be taken to prevent the film from extending into the cathode region. Even then it is difficult to control the getter flashing to such an extent that there are no remaining free particles which can migrate in thetube to the vicinity of the cathode as the tube is handled and operated. a

Accordingly, it is an object of this invention to provide cathode-ray tube electrode structure reducing the chances of contaminating the electron emitting surface with getter parti cles.

In accordance with the invention therefore a convergence cup electrode is made to obstruct the tendency for any getter particles to migrate into the vicinity of the cathode. The convergence electrode provided by:this invention has an outwardly extending rim portion that'serves to reduce the spacing between the convergence electrode and the inner surface of the neck of the tube. Further the beam apertures through the convergence electrode are formed with inwardly extending rims to form ridges inhibiting the passage through the apertures of getter particles that may enter the convergence cup.

For a more detailed description of the invention and its features, reference is made to the single FIGURE of the drawing wherein a foreshortened and broken away cathode ray tube is shown, partly in section.

The cathode-ray tube has an envelope that is evacuated through the glass tube 2 in the stem 3 at the end of the neck portion 4 extending from the flanged section 5. Various electrodes are mounted in the neck 4 and are electrically connected to the terminal pins fifThat electrode 7, closest adjacent the stem 3, generally is a grid or beam forming outer electrode having an inner array including a filament and cathode electron emitting surface exposed through the grid aperture to face the front of the tube (not shown) beyond the flange 5. Other beam forming and'processing electrodes that may be termed second and third grids 8 and 9 are disposed between the cathode surface and the convergence electrode assembly 10. These electrodes are critically spaced and held in position by the glass beads 11, and a'set of grids is provided for each of three electron guns, which commonly use a single convergence cup electrode 10 by means of a set of beam passing apertures l2, 13. The convergence cup electrode 10 is positioned in the neck of the tube by means of a set of snubber springs l4, 15, which ride on the inner surface of the tube envelope.

Extending from the convergence electrode 10 to which it is attached by strip 16 is a getter ring '17. This getter ring 17 is flashed during final stages of evacuation of the tube envelope through tube 2 to form a film on the inner surface of the tube neck 4 in the vicinity of the beginning of the flanged portion 5. It is positioned to avoid as much as feasible any contamination of electrode surfaces. However, in the flashing, it is virtually impossible to avoid the formation of some small getter particles, which might tend to migrate into the cathode emission surface, to thereby poison the emission and greatly shorten the life of a tube.

This undesirable circumstance is substantially eliminated by significantly reducing the chances for any loose getter particles from migrating down into the vicinity of the exposed cathode surface, with the particular construction of the convergence electrode 10 as herein shown.

It may be seen that the flange 20 is extended outwardly from the cylindrical body of the convergence electrode 10, and thereby reduces the spacing between the convergence electrode l0 and the inner surface of the tube neck portion 4. This not only reduces the size of the passageway 19 through which any getter particles could pass from getter 17 through the passageway 19 toward the stem 3 into the vicinity of the exposed emission surface of the cathode, but also confines the spacing so that there is a small likelihood of any particles leaving the getter from having a travel path of such angle that they could get into the electrodes 8, 9, etc., after passing the rim 20. For example, the particles that could get through passageway 19 would under most circumstances fall harmlessly into the bottom of the tube neck about the stem 3 rather than taking a path that would carry them between electrodes 7 and 8 to enter a small grid aperture and contaminate the cathode surface.

In addition, the inwardly flanged rims 21 about apertures 12, 13 prevent any particles that may fall from the getter 17 into the bottom portion of the cup electrode 10 from passing through the beam apertures to progress through the various electrode apertures into the exposed cathode surface inside grid 7. Rather they will be held harmlessly in the bottom of the cup electrode 10. The likelihood of particles directly passing through the apertures 12, 13 when the getter is flashed at such a direct angle that they pass all the way to the exposed cathode surface is small, and it becomes unlikely that the tubes will fail from this contamination possibility when the structure just described is used. The aperture rim structure 21 afforded by this invention eliminates the far greater possibility of residual particles falling into the cup and passing through unrimmed apertures to reach the cathode.

Accordingly, there is provided by this invention a changed structure which cooperates in such a way that a significant problem of cathode poisoning is greatly reduced, and therefore producing far greater tube reliability and far greater efficiency in producing acceptable tubes with long life.

I claim:

1. [n a color picture cathode-ray tube having a plurality of electron guns comprising an envelope for evacuation, a

- sequential array of electrodes in each gun including an electron emitting electrode and a set of beam forming and processing electrodes and including a convergence electrode common to all said guns with structure for mounting and spacing said electrodes within said envelope, the improvement comprising, convergence electrode structure in the form of a cuplike cylindrical body having a generally closed and a generally open end with an outwardly flanged rim at its open end extending outwardly beyond the cylindrical body of the electrode, said envelope being provided with a neck portion for containing the guns being in the form of a cylindrical enclosure with a predetermined inside diameter and said convergence electrode structure having a diameter such that said rim is positioned closely adjacent the inner'surface of said neck portion to thereby serve as an obstruction substantially blocking the passageway through the neck portion, beam conveyance apertures formed in the closed end of said convergence electrode body to have an inwardly extending rim portion circumferentially ridging the apertures, and a getter device mounted in the neck portion on the open end side of said convergence body and on the side opposite that at which said electron emitting electrode is located so that any particles leaving the getter when it is flashed are substantially confined by said convergence body structure to prevent their migration to the vicinity of said electron emitting electrode.

2. An electron gun assembly for a color picture cathode-ray tube having a plurality of electron guns, a sequential array of electrodes in each gun including an electron emitting electrode and a set of beam forming and processing electrodes, a cylindrical convergence electrode receiving an electron beam from all said guns, said convergence electrode having a strucsuch that particles leaving the getter when it is flashed are blocked by the flanged rim on said convergence body structure from migration to the vicinity of said electron emitting electrode. 

1. In a color picture cathode-ray tube having a plurality of electron guns comprising an envelope for evacuation, a sequential array of electrodes in each gun including an electron emitting electrode and a set of beam forming and processing electrodes and including a convergence electrode common to all said guns with structure for mounting and spacing said electrodes within said envelope, the improvement comprising, convergence electrode structure in the form of a cuplike cylindrical body having a generally closed and a generally open end with an outwardly flanged rim at its open end extending outwardly beyond the cylindrical body of the electrode, said envelope being provided with a neck portion for containing the guns being in the form of a cylindrical enclosure with a predetermined inside diameter and said convergence electrode structure having a diameter such that said rim is positioned closely adjacent the inner surface of said neck portion to thereby serve as an obstruction substantially blocking the passageway through the neck portion, beam conveyance apertures formed in the closed end of said convergence electrode body to have an inwardly extending rim portion circumferentially ridging the apertures, and a getter device mounted in the neck portion on the open end side of said convergence body and on the side opposite that at which said electron emitting electrode is located so that any particles leaving the getter when it is flashed are substantially confined by said convergence body structure to prevent their migration to the vicinity of said electron emitting electrode.
 2. An electron gun assembly for a color picture cathode-ray tube having a plurality of electron guns, a sequential array of electrodes in each gun including an electron emitting electrode and a set of beam forming and processing electrodes, a cylindrical convergence electrode receiving an electron beam from all said guns, said convergence electrode having a structure in the form of a cuplike cylindrical body with a generally closed and a generally open end, an outwardly flanged rim extending outwardly from the open end of the convergence electrode beyond the cylindrical body, and a getter device positioned on the open end side of the convergence electrode on the side opposite said electron emitting electrode in a position such that particles leaving the getter when it is flashed are blocked by the flanged rim on said convergence body structure from migration to the vicinity of said electron emitting electrode. 